Inductive balancer for radio direction finders



Se pt. 3, 1935; J A PROCTQR 2,013,1G7

INDUCTIVE BALANCER FOR RADIO DIRECTION FINDERS Filed Dec. 10, 1929 LOOP 72 TO SENSE ANTENNA awuemtoz Patented Sept. 3, 1935 UNH'EE STATES PATENT @FFHQE INDUCTIVE BALANCER FOR RADIO DIRECTION FINDERS Application December 10, 1929, Serial No. 412,989

Claims.

This invention relates to an improved method of inductively balancing radio direction finder loop or coil aerial circuits and more particularly to a novel vario-coupler adapted for use as an 5 inductive balancer in radio direction finder circuits.

It is an object of the present invention to provide an improved balancer which is rugged in construction and mechanically and electrically efficient.

Yet a further object of this invention is to provide such a device which is adapted for use in radio circuits such as in marine direction finders and the like.

Another object of this invention is the provision of an improved variocoupler adapted for use in antenna circuits of radio direction finders.

A still further object of this invention is the provision of an improved inductive balancing method for improving the definition of null points in direction finding by means of radio compasses.

Yet another object of this invention is the provision of an improved method of electromagnetically compensating for spurious voltages generated in coil aerial circuits.

These and other desirable objects and advantages of' the present invention will be described in the accompanying specification and. illustrated in the drawing, a preferred embodiment being shown by way of illustration only, for, since the underlying principles may be incorporated in other specific constructions, it is not intended to be limited to the one here shown, except as such limitations are clearly imposed by the appended claims.

In the drawing, similar numerals refer to like parts throughout the several views, of which Fig. 1 is a rear view of the improved balancing device of the present invention;

Fig. 2 is an elevation of the device with a supporting panel and a portion of the shunt coil shown in section;

Fig. 3 is a view enlarged from Fig. l and in section on line 3--3 of Fig, 1;

Fig. 4 is a view of the rotor and its coils with bakelite cover protection partly removed to show the shield beneath;

Fig. 5 is an elevation of the stator and its cresent-shaped coils;

Fig. 6 is detailed showing of the shield; and

Fig. 7 is a schematic view of the balancer circuit as associated with a direction finder.

In the present invention there is shown a novel balancing mechanism in which the desirable effects are secured by means of variable inductances so constituted and arranged as to secure the necessary effects in a simple and thoroughly efficient manner while permitting the installation to be assembled and set up within a relatively small space. 5

The purpose of the balancer, in its preferred use in radio direction finders of the type shown and claimed in my application No. 227,026 filed May 11, 1928, is to provide the operator with a means for balancing out any disturbing effects 10 due to metal masts, stays, rigging, etc., which effects may cause the direction finder minimum to be broad, so that it is difiicult to take accurate bearings.

The balancer, hereinafter described, sometimes 15 called inductive compensator, is a type of variocoupler, the stator of which comprises two crescent shaped coils m, H, connected respectively in the two down leads from the loop and to its tuning condenser Hi0. In the molded rotor part 20 ll) there are chambered two semi-circular coils 8B, 8! normally connected in parallel. One terminal of both coils 80, 8| is the operating shaft 4! grounded to metallic panel 2 by split cup washer I1; the other terminal is a collector ring 25 88 against which bears the brush E22 connected to the center terminal l2! of the instrument. A lead is brought out from copper shield 9i covering the rotor windings 8D, 8 I, so that this shield also may be connected to the grounded shaft t I Mounted behind the rotor 4 is a coil H0 wound in the groove of a bakelite ring 50 from which are brought out a number of taps l l2l l6. This coil H is called the balancer shunt, since it is connected in shunt to the rotor or antenna 35 windings 86, 8! of the balancer, for the purpose of adjusting the balancing effect to suit each individual installation. The balancer shunt H0, although mounted directly behind the rotor and stator coils, has no resultant magnetic coupling 40 with either, due to the method of connecting these coils, and acts simply to shunt away from the rotor windings 80, 8| of the balancer enough energy to prevent the adjustment of the balancer from being too critical. 45

In the particular use of the variocoupler or balancer, herein referred to by way of example, namely, in the loop or coil aerial circuit of a direction finder, Fig. 7, if the rotating loop re- 50 ceives an undesirable signal voltage due to its coupling With a mast or stay, acting as an antenna, a spurious voltage is set up in the loop circuit, which must be balanced out by a voltage of equal amplitude and opposite phase.

Spurious voltages may enter the coil aerial shunt by:

1. Induction from currents produced from signal waves in surrounding conducting objects, such as stays, stacks, etc., either in the coil aerial itself or in the down leads, or both;

2. Electromagnetic or electrostatic induction or coupling between coil and aerial circuit.

This balancing voltage is induced into the loop circuit by means of the balancer, since the rotating coils 8t), Bi of this instrument are connected to the open antenna, Fig. '7, normally used for the determination of the sense of direction. The amplitude of the balancing voltage is determined by the magnetic coupling between the said rotating coils and stationary coils Hi, 1 i and the phase of the induced voltage can be shifted 180 degrees by rotating the balancer pointer by knob it through 180 degrees.

For the balancer shunt H0 there are five taps, Fig. 1, numbered H2, H3, H4, H5 and H6, and the inductance between each is given in the following table.

Taps Inductances lvlicrohemies 112-116 1250 113-116 875 112-115 590 114-116 475 113-115 340 112-114 200 115-116 114-115 105 113-114 75 112-113 05 The use of these values will be understood from the diagram, Fig. 7, from Fig. 1, and the following, it being kept in mind that their function is to shunt away from rotor windings SB, 8!, sufficient incoming energy to prevent the balancing adjustment by shaft 41 from becoming too critical, and that coil iii! has no magnetic coupling with any of the coils of the stator or retor. The grounding of the sense antenna, Fig. '7, is effected by way of adjustable balancer shunt coil 6 iii which is connected to the sense antenna as shown. The above values of portions of coil Mb are obtained by adjustments of the flexible leads i23l24 of Fig. l, which, in series with one another and with desired portions of coil Iii], connect rotor coils 88, 8|, by way of collector ring 86 and wiping contact I22, to the sense antenna to which coil HE is connected, as above. That is, lead 623 is connected at one end at center, Figs. 1 and 3, to wiping contact I22, and the other end of this lead E23 is connected to any desired one of terminals H2i 16 of coil i it. Similarly one end of lead I24, which, Fig. 7, connects coil M9 to ground, is connected to another terminal of coil tit; and the adjacent ends of leads Hit-i2 5 include between them any appropriate one of the above ten values of inductance of coil Ht. A convenient ground for lead 524 is the same as for lead 92, Fig. 6. of shield ti, 1. e., panel 25 by way of shaft M and screw 49a, Figs. 34.

The adjustment of the balancer shunt lib should be carried out during calibration, except in those cases where the balancer is added after calibration has been completed. In such cases, the adjustment will have to be made at the dock, in the case of a ship installation.

The amount of balance energy required for a spark signal will in some cases be different from that of. an I. C. W. signal at the same angle and will vary with the decrement of the spark signal. The maximum amount of balance energy is obtainable with the balancer set at 90 degrees and 2'70 degrees and the minimum balance energy at 0 degrees and degrees. However, the value of the energy obtainable will be limited by the size of the sense antenna and the adjustment of the shunt. Maximum balance energy will be obtained with the shunt I IEI circuit open and minimum balance energy with leads to the shunt I I9 connected to taps H2! l3 Fig. 1. Intermediate values may be obtained by other connections as indicated above. The shunt coil 1 Hi must be adjusted so that the balancer will bring the minimum signal to zero at the lubber line bearing where the minimum is broadest. This bearing can be ascertained if it is possible to swing the ship, and after it has been determined, the shunt i it should be adjusted so that the balancer pointer operated by knob It! reads about 65 degrees either side of 0 degrees, allowing the remaining 25 degrees to take care of spark or other signals for operating under otherwise inoperativecondi tions.

l/Vhen taking bearings, the pointer for balancer knob it) should be set at 0 and the loop swung to minimum signalstrength. The balancer should then be adjusted for sharpest minimum and the loop readjusted until signal strength falls to zero. In most cases, the minimum split, with balance correctly adjusted, should be Within 1 degree for a strong signal.

Referring now to the drawing, the improved balancer variocoupler of' the present invention comprises a rotor control member 10, a metallic supporting panel 20, insulating stator support 30, insulating rotor support 40, insulating shunt coil frame so, and frame supports 60, 6| together with the associated coils, leads and terminals, as will be described more fully hereinafter.

The control member includes a knob l 0, having a bossed extension 12 tapped to receive portions M of shaft member 13, M. Member 13 is adapted to rotate freely in aperture 2| of metal panel 253 and is provided with reentrant shouldered sections M, l5 adapted to abutand fit in looking engagement portions of members H] and 12. The rotor shaft proper M continuing from I3 is freely movable in apertured .metallic bushing 3l-0f the statorstructure 30, etc. A split cup washer I! and an extra washer I8 are interposed between bushing 31 and shaft-member 13, the cup washer being contacted with metal panel 20 to furnish a ground connection for therotor shaft 41 for purposes to be described more in detail.

The insulating stator support 30 comprises an elongated body portion 32 having a semi-circular end portion an opposite end 34, and shelf portions 35 apertured to receive metallic eyelets 6|.

, The support 38 has a depending flange 3t abutting and in bearing engagement with the metallic panel 20 of an instrument board upon which the balancer structure is mounted by means of screws into correspondingly configured l5. An inner circumferential depression 31, Fig. 5, in support 30, and opposed arcuate depressions 38, all in the top of support 30, form crescent shaped stator cores 39 and a central core 39 which is in the shape of a centrally constricted truncated ellipsoid.

Respectively nested in the two crescent-shaped depressions 31 and 38 in support 30 are a pair of crescent shaped stator, coils 70, ll, wound in any suitable manner and provided with leads l2, l3, l t, l5 to terminals 75, ll, l8, '99 from the loop and tuning condenser N36. The circuit diagram in Fig. '7 shows the interrelation of these parts, and reference is had thereto.

The stator support 30 is preferably made of bakelite, molded around the metallic parts including the bushing 31, the terminals 16, ll, l8, l9, and the eyelets 6|. While bakelite is a preferred material, other insulating condensation products or ceramics, such as Isolantite, porcelain, or Lavite may be made use of, or natural materials, such as slate or suitably treated woods, may be suitably configured to serve the desired purpose.

In addition, the stator support 30 is provided with a plurality of embedded nuts 25 adapted to r ceive suitable screws l6, whereby to secure the balancer structure to the panel 20 by way of support 38.

Referring now to the rotor structure, supported by the above stator structure, this comprises, Fig. 4, a circular insulating base portion 40, having two semicircular grooves 43, between external and internal circular flanges 44, 45. Two semicircular pancake type rotor coils, 80, 8|, are mounted in said grooves. Centrally of the rotor and said coils, there is embedded a polygonally shaped metallic bushing 46 through which rotor shaft li passes. This bushing 46 is provided with a flat bearing surface adapted to abut a cooperating surface on the upper portion of bushing 3| embedded in the stator structure.

The rotor member 40 is provided with an integral boss portion 41 having a depression 48 coaxial with and receiving bushing 45 and adapted to receive the upper end of the rotor shaft M. This upper end of the shaft is locked to the rotor structure by means of a pair of set screws 49 tapped into the member ll. By means of the locking screws the shaft is maintained coaxial with the rotor. As will be noted from an inspection of the drawing, one of the screws 39 is provided with a headed portion 59a to permit the engagement of leads from one end of each of the parallel coils 80, 8!, thereby grounding them to the metal panel 20 through the rotor shaft 4| and its portions l3 and split cup washer I1. These leads from coils 88, 8| are designated respectively 82 and 83, and are shown in the circuit diagram of Fig. 7.

The opposite ends of the coils 80, 8| are provided with leads 84, 85 which are passed through apertures 85 in the coil support member and led up outside of boss 47 to a common terminal 8'! which is integrally connected or soldered to collector ring 88 embedded in the upper surface of the boss Q7 of rotor support 41]. By this construction it will be seen that the rotor coils and 8| are connected in parallel, one common end being connected to the ground (panel 20) through the rotor shaft 4|, and the other common end being connected to the collector ring 88.

The rotor coils 80, are maintained in their respective channels and prevented from falling out, in the following manner. An insulating member, such as a paper washer 9B, is disposed over the exposed surfaces of the coils and the adjacent portions of the rotor 40, which are preferably flush with the coils. A static shield 9i (constructed as in Fig. 4) is next laid on top of the washer Sill and grounded to the shaft M by means of a lead 92, Fig. 6, connected to screw head 49a, Figs. 3, l. The member 9i comprises a plurality of integral circular segments 93, Fig. 6, configured to the coils, 8!], 8i and formed with gaps 9 5 between the several segments. The gaps prevent eddy currents normally met with in continuous masses of metal subjected to high frequency currents, and the grounding of the shield as a whole prevents any undesired static or capacity coupling between the stator and rotor coils, i. e., between the sense antenna and the loop. Over the static shield 9i is placed an insulating member of bakelite dilecto or other suitable insulating material of suitable strength. This member 95 is forced into and held in juxtaposition with the rotor coils 8B, 8i and the interposed washer 90 and static shield 9|, by means of a plurality of flat head screws 96, flush with the surface of member 95, and passing through suitable apertures in section 43 of the rotor support Ml. The screws and associated parts are preferably made of brass or other diamagnetic metals, to prevent any undesired electrical efiects. By the construction just described, the rotor coils 89, 8! are permanently fixed in their respective positions in such a manner as to insure a maximum of efficiency both in fabrication and in operation of the completed device when installed. The gap between the rotor coils 80, 8! and the stator coils it, H is fixed by the arrangement of the bushings 3i and it and said gap may be adjusted by set screws as at 39a, Fig. 3, which are adapted to vary the distance or gap between the stator and rotor coils by varying the stress of the portion 13 of rotor shaft 4! on split cup washer H with which the portion [3 is in wiping spring-contact.

While the rotor coils 8i! and Si have been shown as having a common ground, (shaft M and panel 29) placing them in parallel, they may be operated in series by opening the circuit in one of the legs, as by disconnecting lead 8'3, without af fecting the operation of the device. In fact, for some installations, it may be desired to operate these rotor coils in series rather than in parallel in order to decrease the effective coupling there between.

The operation of the stator and rotor coils has been indicated previously, and will be readily understood from the circuit diagram shown in Fig. '7 wherein is disclosed the fact that the currents from the loop passing through the stator coils are variably reacted upon by antenna currents passing through the rotor coils. The rotor coils may be revolved through an axis of 360 degrees, and can exert a maximum of inductive effect on the stator coils. Or by a revolution through only 90 degrees, their effect can be progressively brought to zero. This flexibility permits extremely nice balancing of the received signals, the absence of which would result in broad nulls, or nulls which are not degrees apart. And as to the vital feature of narrowness of null points which determines the accuracy of direction finding, it has been proved that the above crescent shape of the stator coils causes a substantially narrower null point than ever before effected, that highly beneficial result being due to the fact that the coils of such shape produce an improved sine operation which results in such electrical symmetry of the loop circuit as to cause the improved narrow null point of reception for greatly increased accuracy of direction finding.

To secure optimum adjustment of the antenna energy, the improved system of the present invention comprehends the inclusion of more inductance in the sense or antenna circuit than in the loop circuit. The particular value of inductance I Iii, which is to be inserted in the sense antenna circuit is determined by calibration of the instrument at the time of its installation. The theoretical factors involved in the insertion of the balancing shunt I I9 in the sense or rotor circuit, have been discussed previously and the preferred structure of the present invention will now be described, it being understood that any modifications thereof are intended to be covered by the present description, which, of necessity cannot be extended to cover all possible variations of structure.

This balancer shunt coil structure, designated generally by the numeral 50, comprises an elongated insulating support 5I, having sides 52, end 53 and converging front sides 54 terminating in the slotted aperture 55. At the junction of portions 52 and 53, the member is apertured to receive headed screws 62 cooperating with supporting posts SI, which in turn are mounted in members Bia of the stator support 48. These posts El may be of any suitable non-magnetic metal or structural insulating material and are secured in apertures Gla, by crimping or in any other suitable manner.

Member 60 is provided with a shouldered cut out portion 63 adapted to receive the slotted portion 55 of the shunt coil support EI. Member 53 is secured to the stator support 37.! by means of the headed screw 64 passing upwardly through the stator support.

The support 5I is centrally apertured to receive the bossed portion 4'! of the rotor Ml and its associated parts, as will be described more in detail hereinafter.

superposed on the support 5! and secured thereto in any suitable manner as by eyelets 56 is the insulating member 50. This member is provided with a raised annulus 58 set in from its edge to form with 5| an annular coil-receiving channel 59, adapted to receive the balancer shunt coil H0. This coil is wound to give any desired inductance, say of the order of 1250 microhenries, and is provided with taps connected to terminals H2, H3, H4, H5, H6, by means of suitable leads indicated generally at In. The terminals comprise the usual plurality of nuts and lock washers, and are supported in insulating member 58 as shown. The various combinations of inductances obtainable by coil III), have been previously described, by way of example, as it will readily be apparent that any desired value may be obtained by varying the turn distance between taps.

Centrally of its perimeter, the member 50 is tapped to receive the terminal H8, which comprises the usual headed screw II9, lock washer I20 and nuts I2I. The screw is inverted to permit the brush I22 to be inserted between its head and the inner side of terminal support 51. This brush is in sliding contact with the collector ring 88, and is connected through terminal II8 to the jumper or flexible connector I23, and the sense antenna lead. Another jumper I24, is connected to any other of the shunt coil taps, as H4, and to ground, thus interposing a desired inductance (200 microhenries as here shown in Fig. l) in shunt to the rotor or sense antenna circuit. The function of this inserted inductance having been fully discussed before, the construction is self-explanatory and needs no further amplification.

If, in a given installation, it is'found thatno balancing shunt connection is needed, the shunt coil H0 may be cut oil? the sense circuit by directly coupling the rotor coils 80, BI to the sense antenna by omitting the jumper I23. I

It will now be seen that there has been provided an improved method of introducing a balancing inductance in a sense antenna circuit of a radio direction finder, as well as an improved variocoupler and balancer for such devices, the whole being simple of construction, and susceptible of varying the balancing inductance of the sense circuit by suitably connecting a pair of associated jumpers or flexible connectors to the sense antenna and the balancer shunt coil.

What is claimed is:

V l. A radio direction finder inductive balancer including a stator having a plurality of crescent shaped coils a metallic inserted bearing located centrally in said stator, and rotor having a plurality of arcua-te coils in inductively coupled relation to said crescent shaped coils and an inserted shaft for rotating the rotor located within and. passing through the inserted bearing in said stator.

2. A radio loop direction finder inductive balancer which includes rotor and stator coils for connection to the loop and sense antenna; molded insulating supports for said coils; a metallic panel; means securing the stator-support to said panel; means securing the rotor-support to the stator-support said means comprising a metallic insert having an aperture; a balancer shunt coil and an insulating support therefor and means securing said support to the stator support; a shaft extending thru the panel and through the aperture in said metallic insert in said stator, said shaft being electrically connected to said panel and secured for rotation to the rotor-support; means electrically connecting the rotor-coils to said shunt coil; and meanselectrically connecting the shunt coil and the rotor-coils to said panel by way of said shaft.

3. A radio loop direction finder inductive balancer which includes rotor and stator coils for connection to the loop and sense antenna; molded insulating supports for said coils; a panel carrying the stator support; means securing the rotor-support to the stator-support said means comprising a metallic insert having an aperture; a shaft extending thru said panel and then thru the aperture of said insert, a balancer shunt coil and an insulating support therefor secured to said stator-support; means electrically connecting the rotor-coils to said shunt coil; and means electrically connecting the shunt coil and the rotor-coils to said shaft.

4. A radio loop direction finder inductive balancer which includes rotor and stator coils for connection to the loop and sense antenna; moldedinsulating supportsfor said coils; a balancer shunt inductance facing the'opposite side of the rotor coils from the stator coils, a static shield between the coils of the stator and rotor; an operating shaft extending thru the stator-coilsupport, the static shield and the rotor coils and secured to the rotor-coil support; an electrical connection between the rotor-coils and the balancer shunt inductance; and electrical connections respectively from the balancer shunt inductance, the rotor coils and the static shield to that portion of the shaft which extends beyond the stator support thru the rotor coils and static shield.

5. A radio loop direction finder inductive balancer which includes rotor and stator coils for connection to the loop and sense antenna; a rotatable molded insulating support for the rotor coils; a balancer shunt inductance facing the 10 opposite side of the rotor coils from the stator coils; a molded insulating support for the stator coils said supports having a metallic insert provided with an aperture; an opera-ting shaft extending thru the aperture in said insert of the stator-coil-support and connected to rotate the rotor coil support; a lead from the shunt inductance to said shaft; and another lead, a Wiping contact and a collector ring connecting said shunt inductance to the rotor coils.

JOHN ALBERT PROCTOR. 

